A gut microbial peptide and molecular mimicry in the pathogenesis of type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of pancreatic ß-cells. One of the earliest aspects of this process is the development of autoantibodies and T cells directed at an epitope in the B-chain of insulin (insB:9-23). Analysis of microbial protein sequences with homology to the insB:9-23 sequence revealed 17 peptides showing >50% identity to insB:9-23. Of these 17 peptides, the hprt4-18 peptide, found in the normal human gut commensal Parabacteroides distasonis, activated both human T cell clones from T1D patients and T cell hybridomas from nonobese diabetic (NOD) mice specific to insB:9-23. Immunization of NOD mice with P. distasonis insB:9-23 peptide mimic or insB:9-23 peptide verified immune cross-reactivity. Colonization of female NOD mice with P. distasonis accelerated the development of T1D, increasing macrophages, dendritic cells, and destructive CD8+ T cells, while decreasing FoxP3+ regulatory T cells. Western blot analysis identified P. distasonis-reacting antibodies in sera of NOD mice colonized with P. distasonis and human T1D patients. Furthermore, adoptive transfer of splenocytes from P. distasonis-treated mice to NOD/SCID mice enhanced disease phenotype in the recipients. Finally, analysis of human children gut microbiome data from a longitudinal DIABIMMUNE study revealed that seroconversion rates (i.e., the proportion of individuals developing two or more autoantibodies) were consistently higher in children whose microbiome harbored sequences capable of producing the hprt4-18 peptide compared to individuals who did not harbor it. Taken together, these data demonstrate the potential role of a gut microbiota-derived insB:9-23-mimic peptide as a molecular trigger of T1D pathogenesis.

Unlocking the Power of Magnesium Batteries: Synergistic Effect of InSb-C Composites to Achieve Superior Electrochemical Performance.

Pure magnesium anode used in rechargeable magnesium batteries (RMB) exhibits high theoretical capacity but has been challenged by the passivation issue with conventional electrolytes. Alloy-type anodes have the potential to surpass this issue and have attracted increasing attention. However, the kinetic performance and stabilities of conventional alloy anodes are still constrained. In this study, the InSb-10%C anode is synthesized by a two-step high-energy ball milling process. The InSb-10%C anode exhibits a remarkably high capacity of up to 448 mA h g-1, significantly improved cycle performance (234 mA h g-1 at 100 cycles) and rate performance (168 mA h g-1 at 500 mA g-1). The above-mentioned superior performance of the InSb-10%C anode for RMBs is attributed to the cellular graphitized amorphous carbon composite structure (CGA) which effectively refines the particle size and restricts the volume expansion. Additionally, the reduced surface electron density of InSb combined with the high conductivity resulting from graphitization enhances the Mg2+ diffusion performance. Notably, the InSb-10%C anode demonstrates good compatibility with conventional halogen-free salt ether-based electrolytes in the full battery configuration.

Thermal scanning probe and laser lithography for patterning nanowire based quantum devices.

Semiconductor nanowire (NW) quantum devices offer a promising path for the pursuit and investigation of topologically-protected quantum states, and superconducting and spin-based qubits that can be controlled using electric fields. Theoretical investigations into the impact of disorder on the attainment of dependable topological states in semiconducting nanowires with large spin-orbit coupling andg-factor highlight the critical need for improvements in both growth processes and nanofabrication techniques. In this work, we used a hybrid lithography tool for both the high-resolution thermal scanning probe lithography and high-throughput direct laser writing of quantum devices based on thin InSb nanowires with contact spacing of 200 nm. Electrical characterization demonstrates quasi-ballistic transport. The methodology outlined in this study has the potential to reduce the impact of disorder caused by fabrication processes in quantum devices based on 1D semiconductors.

Stemless InSb nanowire networks and nanoflakes grown on InP.

Among the experimental realization of fault-tolerant topological circuits are interconnecting nanowires with minimal disorder. Out-of-plane indium antimonide (InSb) nanowire networks formed by merging are potential candidates. Yet, their growth requires a foreign material stem usually made of InP-InAs. This stem imposes limitations, which include restricting the size of the nanowire network, inducing disorder through grain boundaries and impurity incorporation. Here, we omit the stem allowing for the growth of stemless InSb nanowire networks on an InP substrate. To enable the growth without the stem, we show that a preconditioning step using arsine (AsH3) is required before InSb growth. High-yield of stemless nanowire growth is achieved by patterning the substrate with a selective-area mask with nanohole cavities, containing restricted gold droplets from which nanowires originate. Interestingly, these nanowires are bent, posing challenges for the synthesis of interconnecting nanowire networks due to merging failure. We attribute this bending to the non-homogeneous incorporation of arsenic impurities in the InSb nanowires and the interposed lattice-mismatch. By tuning the growth parameters, we can mitigate the bending, yielding large and single crystalline InSb nanowire networks and nanoflakes. The improved size and crystal quality of these nanostructures broaden the potential of this technique for fabricating advanced quantum devices.

Moiré Pattern Formation in Epitaxial Growth on a Covalent Substrate: Sb on InSb(111)A.

Structural moiré superstructures arising from two competing lattices may lead to unexpected electronic behavior. Sb is predicted to show thickness-dependent topological properties, providing potential applications for low-energy-consuming electronic devices. Here we successfully synthesize ultrathin Sb films on semi-insulating InSb(111)A. Despite the covalent nature of the substrate, which has dangling bonds on the surface, we prove by scanning transmission electron microscopy that the first layer of Sb atoms grows in an unstrained manner. Rather than compensating for the lattice mismatch of -6.4% by structural modifications, the Sb films form a pronounced moiré pattern as we evidence by scanning tunneling microscopy. Our model calculations assign the moiré pattern to a periodic surface corrugation. In agreement with theoretical predictions, irrespective of the moiré modulation, the topological surface state known on a thick Sb film is experimentally confirmed to persist down to small film thicknesses, and the Dirac point shifts toward lower binding energies with a decrease in Sb thickness.

Heteroepitaxial Growth of InBi(001).

InBi is a topological nodal line semimetal with strong spin-orbit coupling. It is epitaxially compatible with III-V semiconductors and, hence, an attractive material for topological spintronics. However, growth by molecular beam epitaxy (MBE) is challenging owing to the low melting point of InBi and the tendency to form droplets. We investigate approaches for epitaxial growth of InBi films on InSb(001) substrates using MBE and periodic supply epitaxy (PSE). It was not possible to achieve planar, stoichiometric InBi heteroepitaxy using MBE growth over the parameter space explored. However, pseudomorphic growth of ultra-thin InBi(001) layers could be achieved by PSE on InSb(001). A remarkable change to the in-plane epitaxial orientation is observed.

One-Pot Colloidal Synthesis Enables Highly Tunable InSb Short-Wave Infrared Quantum Dots Exhibiting Carrier Multiplication.

Colloidal quantum dots (CQDs) are emerging materials for short-wave infrared (SWIR, ≈1100-3000 nm) photodetectors, which are technologically important for a broad array of applications. Unfortunately, the most developed SWIR CQD systems are Pb and Hg chalcogenides; their toxicity and regulated compositions limit their applications. InSb CQD system is a potential environmentally friendly alternative, whose bandgap in theory, is tunable via quantum confinement across the SWIR spectrum. However, InSb CQDs are difficult to exploit, due to their complex syntheses and uncommon reactive precursors, which greatly hinder their application and study. Here, a one-pot synthesis strategy is reported using commercially available precursors to synthesize-under standard colloidal synthesis conditions-high-quality, size-tunable InSb CQDs. With this strategy, the large Bohr exciton radius of InSb can be exploited for tuning the bandgap of the CQDs over a wide range of wavelengths (≈1250-1860 nm) across the SWIR region. Furthermore, by changing the surface ligands of the CQDs from oleic acid (OA) to 1-dodecanthiol (DDT), a ≈20-fold lengthening in the excited-state lifetime, efficient carrier multiplication, and slower carrier annihilation are observed. The work opens a wide range of SWIR applications to a promising class of Pb- and Hg-free CQDs.

Josephson Diode Effect in High-Mobility InSb Nanoflags.

We report nonreciprocal dissipation-less transport in single ballistic InSb nanoflag Josephson junctions. Applying an in-plane magnetic field, we observe an inequality in supercurrent for the two opposite current propagation directions. Thus, these devices can work as Josephson diodes, with dissipation-less current flowing in only one direction. For small fields, the supercurrent asymmetry increases linearly with external field, and then it saturates as the Zeeman energy becomes relevant, before it finally decreases to zero at higher fields. The effect is maximum when the in-plane field is perpendicular to the current vector, which identifies Rashba spin-orbit coupling as the main symmetry-breaking mechanism. While a variation in carrier concentration in these high-quality InSb nanoflags does not significantly influence the supercurrent asymmetry, it is instead strongly suppressed by an increase in temperature. Our experimental findings are consistent with a model for ballistic short junctions and show that the diode effect is intrinsic to this material.

Fabrication and characterization of InSb nanosheet/hBN/graphite heterostructure devices.

Semiconductor InSb nanosheet/hexagonal boron nitride (hBN)/graphite trilayers are fabricated, and single- and double-gate devices made from the trilayers are realized and characterized. The InSb nanosheets employed in the trilayer devices are epitaxially grown, free-standing, zincblende crystals and are in micrometer lateral sizes. The hBN and graphite flakes are obtained by exfoliation. Each trilayer is made by successively stacking an InSb nanosheet on an hBN flake and on a graphite flake using a home-made alignment stacking/transfer setup. The fabricated single- and double-gate devices are characterized by electrical and/or magnetotransport measurements. In all these devices, the graphite and hBN flakes are employed as the bottom gates and the gate dielectrics. The measurements of a fabricated single bottom-gate field-effect device show that the InSb nanosheet in the device has an electron field-effect mobility of âˆ¼7300 cm2V-1s-1and a low gate hysteresis of âˆ¼0.05 V at 1.9 K. The measurements of a double-gate Hall-bar device show that both the top and the bottom gate exhibit strong capacitive couplings to the InSb nanosheet channel and can thus tune the nanosheet channel conduction effectively. The electron Hall mobility in the InSb nanosheet of the Hall-bar device is extracted to be larger than 1.1 × 104cm2V-1s-1at a sheet electron density of âˆ¼6.1 × 1011cm-2and 1.9 K and, thus, the device exhibits well-defined Shubnikov-de Haas oscillations.

The Comparison of InSb-Based Thin Films and Graphene on SiC for Magnetic Diagnostics under Extreme Conditions.

The ability to precisely measure magnetic fields under extreme operating conditions is becoming increasingly important as a result of the advent of modern diagnostics for future magnetic-confinement fusion devices. These conditions are recognized as strong neutron radiation and high temperatures (up to 350 °C). We report on the first experimental comparison of the impact of neutron radiation on graphene and indium antimonide thin films. For this purpose, a 2D-material-based structure was fabricated in the form of hydrogen-intercalated quasi-free-standing graphene on semi-insulating high-purity on-axis 4H-SiC(0001), passivated with an Al2O3 layer. InSb-based thin films, donor doped to varying degrees, were deposited on a monocrystalline gallium arsenide or a polycrystalline ceramic substrate. The thin films were covered with a SiO2 insulating layer. All samples were exposed to a fast-neutron fluence of ≈7×1017 cm-2. The results have shown that the graphene sheet is only moderately affected by neutron radiation compared to the InSb-based structures. The low structural damage allowed the graphene/SiC system to retain its electrical properties and excellent sensitivity to magnetic fields. However, InSb-based structures proved to have significantly more post-irradiation self-healing capabilities when subject to proper temperature treatment. This property has been tested depending on the doping level and type of the substrate.

Reducing the thermal deformation of InSb crystal by using double-bounce HHRMs in the TPS tender X-ray absorption spectroscopy beamline.

The Taiwan Photon Source (TPS) with high brightness and energy tunability is suitable for applications in spectroscopy. The tender X-ray absorption beamline will be optimized for X-ray absorption spectroscopy measurements using a bending-magnet source in a unique photon energy range (1.7-10 keV) and two crystal pairs [InSb(111) and Si(111)] separated using back-to-back double-crystal monochromators (DCMs). InSb crystals are typically used in the lower photon energy range of 1.7-3.5 keV. However, the poor thermal conductivity of InSb crystals leads to severe deformation. This factor should be considered when the monochromator is installed on a tender X-ray beamline in a storage ring with a high power density. There are many approaches to reducing the thermal load on the first crystal of a DCM. Double-bounce high harmonics rejection mirrors in front of the DCM serve not only to reduce the high-order harmonics but also to absorb considerable quantities of heat. Two coating stripes on the silicon surfaces with a variable incident angle will be key to solving the thermal load on this beamline.

Flexible infrared photodetector based on indium antimonide nanowire arrays.

Narrow bandgap semiconductors like indium antimonide (InSb) are very suitable for high-performance room temperature infrared photodetectors, but the fragile nature of the wafer materials hinders their application as flexible/wearable devices. Here, we present a method to fabricate a photodetector device of assembled crystalline InSb nanowire (NW) arrays on a flexible substrate that balances high performance and flexibility, facilitating its application in wearable devices. The InSb NWs were synthesized by means of a vapor-liquid-solid technique, with gold nanoclusters as seeding particles. The morphological and crystal properties were investigated using scanning electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy, which revealed the unique spike shape and high crystallinity with (111) and (220) planes of InSb NWs. The flexible infrared photodetector devices were fabricated by transferring the NWs onto transparent and stretchable polydimethylsiloxane substrate with pre-deposited gold electrodes. Current versus time measurement of the photodetector devices under light showed photoresponsivity and sensitivity to mid-infrared at bias as low as 0.1 V while attached to curved surfaces (suitable for skin implants). A high-performance NW device yielded efficient rise and decay times down to 1 s and short time lag for infrared detection. Based on dark current, calculated specific detectivity of the flexible photodetector was 1.4 × 1012Jones. The performance and durability render such devices promising for use as wearable infrared photodetectors.

Spin Transport in Ferromagnet-InSb Nanowire Quantum Devices.

Signatures of Majorana zero modes (MZMs) have been observed in semiconductor nanowires (NWs) with a strong spin-orbital interaction (SOI) with proximity-induced superconductivity. Realizing topological superconductivity and MZMs in this platform requires eliminating spin degeneracy by applying a magnetic field. However, the field can adversely impact the induced superconductivity and places geometric restrictions on the device. These challenges could be circumvented by integrating magnetic elements with the NWs. Here, we report the first experimental investigation of spin transport across InSb NWs with ferromagnetic (FM) contacts. We observe signatures of spin polarization and spin-dependent transport in the quasi-one-dimensional ballistic regime. Moreover, we show that electrostatic gating tunes the observed magnetic signal and reveals a regime where the device acts as a spin filter. These results open an avenue toward developing MZM devices with spin degeneracy lifted locally without external fields. They could also enable spin-based devices that leverage spin-orbital states in quantum wires.

Retro-inverso D-peptides as a novel targeted immunotherapy for Type 1 diabetes.

Over the past four decades, the number of people with Type 1 Diabetes (T1D) has increased by 4% per year, making it an important public health challenge. Currently, no curative therapy exists for T1D and the only available treatment is insulin replacement. HLA-DQ8 has been shown to present antigenic islet peptides driving the activation of CD4+ T-cells in T1D patients. Specifically, the insulin peptide InsB:9-23 activates self-reactive CD4+ T-cells, causing pancreatic beta cell destruction. The aim of the current study was to identify retro-inverso-d-amino acid based peptides (RI-D-peptides) that can suppress T-cell activation by blocking the presentation of InsB:9-23 peptide within HLA-DQ8 pocket. We identified a RI-D-peptide (RI-EXT) that inhibited InsB:9-23 binding to recombinant HLA-DQ8 molecule, as well as its binding to DQ8 expressed on human B-cells. RI-EXT prevented T-cell activation in a cellular antigen presentation assay containing human DQ8 cells loaded with InsB:9-23 peptide and murine T-cells expressing a human T-cell receptor specific for the InsB:9-23-DQ8 complex. Moreover, RI-EXT blocked T-cell activation by InsB:9-23 in a humanized DQ8 mice both ex vivo and in vivo, as shown by decreased production of IL-2 and IFN-γ and reduced lymphocyte proliferation. Interestingly, RI-EXT also blocked lymphocyte activation and proliferation by InsB:9-23 in PBMCs isolated from recent onset DQ8-T1D patients. In summary, we discovered a RI-D-peptide that blocks InsB:9-23 binding to HLA-DQ8 and its presentation to T-cells in T1D. These findings set the stage for using our approach as a novel therapy for patients with T1D and potentially other autoimmune diseases.

Room-Temperature Ferromagnetism in InSb-Mn Nanowires.

The successful synthesis of one-dimensional nanostructures of a narrow band gap semiconductor, exhibiting a ferromagnetic response at room temperature, is reported. High-quality nanowires of InSb-Mn have been produced by template-assisted pulse electrodeposition. Detailed structural and spectroscopic characterizations revealed good crystallinity, a narrow size distribution of the nanostructures, and the ability to control the Mn doping level. The dominating magnetic response at a cryogenic temperature evolves with an increasing Mn concentration from paramagnetic through antiferromagnetic to ferromagnetic. A robust ferromagnetic response of InSb nanowires doped with 2.5% at. of Mn is retained up to a Curie temperature of nearly 500 K.

Ballistic InSb Nanowires and Networks via Metal-Sown Selective Area Growth.

Selective area growth is a promising technique to realize semiconductor-superconductor hybrid nanowire networks, potentially hosting topologically protected Majorana-based qubits. In some cases, however, such as the molecular beam epitaxy of InSb on InP or GaAs substrates, nucleation and selective growth conditions do not necessarily overlap. To overcome this challenge, we propose a metal-sown selective area growth (MS SAG) technique, which allows decoupling selective deposition and nucleation growth conditions by temporarily isolating these stages. It consists of three steps: (i) selective deposition of In droplets only inside the mask openings at relatively high temperatures favoring selectivity, (ii) nucleation of InSb under Sb flux from In droplets, which act as a reservoir of group III adatoms, done at relatively low temperatures, favoring nucleation of InSb, and (iii) homoepitaxy of InSb on top of the formed nucleation layer under a simultaneous supply of In and Sb fluxes at conditions favoring selectivity and high crystal quality. We demonstrate that complex InSb nanowire networks of high crystal and electrical quality can be achieved this way. We extract mobility values of 10 000-25 000 cm2 V-1 s-1 consistently from field-effect and Hall mobility measurements across single nanowire segments as well as wires with junctions. Moreover, we demonstrate ballistic transport in a 440 nm long channel in a single nanowire under a magnetic field below 1 T. We also extract a phase-coherent length of ∼8 µm at 50 mK in mesoscopic rings.

High Mobility Stemless InSb Nanowires.

High aspect-ratio InSb nanowires (NWs) of high chemical purity are sought for implementing advanced quantum devices. The growth of InSb NWs is challenging, generally requiring a stem of a foreign material for nucleation. Such a stem tends to limit the length of InSb NWs and its material becomes incorporated in the InSb segment. Here, we report on the growth of chemically pure InSb NWs tens of microns long. Using a selective-area mask in combination with gold as a catalyst allows complete omission of the stem, thus demonstrating that InSb NWs can grow directly from the substrate. The introduction of the selective-area mask gives rise to novel growth kinetics, demonstrating high growth rates and complete suppression of layer deposition on the mask for Sb-rich conditions. The crystal quality and chemical purity of these NWs is reflected in the significant enhancement of low-temperature electron mobility, yielding an average of 4.4 × 104 cm2/(V s), compared to previously studied InSb NWs grown on stems.

Two-Dimensional Quantum Transport in Free-Standing InSb Nanosheets.

Low-dimensional narrow band gap III-V compound semiconductors, such as InAs and InSb, have attracted much attention as one of promising platforms for studying Majorana zero modes and non-Abelian statistics relevant for topological quantum computation. So far, most of experimental studies were performed on hybrid devices based on one-dimensional semiconductor nanowires. In order to build complex topological circuits toward scalable quantum computing, exploring high-mobility two-dimensional (2D) III-V compound electron system with strong spin-orbit coupling is highly desirable. Here, we study quantum transport in high-mobility InSb nanosheet grown by molecular-beam epitaxy. The observations of Shubnikov-de Hass oscillations and quantum Hall states, together with the angular dependence of magnetotransport measurements, provide the evidence for the 2D nature of electronic states in InSb nanosheet. The presence of strong spin-orbit coupling in the InSb nanosheet is verified by the low-field magnetotransport measurements, characterized by weak antilocalization effect. Finally, we demonstrate the realization of high-quality InSb nanosheet-superconductor junctions with transparent interface. Our results not only advance the study of 2D quantum transport but also open up opportunities for developing hybrid topological devices based on 2D semiconducting nanosheets with strong spin-orbit coupling.

Hard Superconducting Gap in InSb Nanowires.

Topological superconductivity is a state of matter that can host Majorana modes, the building blocks of a topological quantum computer. Many experimental platforms predicted to show such a topological state rely on proximity-induced superconductivity. However, accessing the topological properties requires an induced hard superconducting gap, which is challenging to achieve for most material systems. We have systematically studied how the interface between an InSb semiconductor nanowire and a NbTiN superconductor affects the induced superconducting properties. Step by step, we improve the homogeneity of the interface while ensuring a barrier-free electrical contact to the superconductor and obtain a hard gap in the InSb nanowire. The magnetic field stability of NbTiN allows the InSb nanowire to maintain a hard gap and a supercurrent in the presence of magnetic fields (∼0.5 T), a requirement for topological superconductivity in one-dimensional systems. Our study provides a guideline to induce superconductivity in various experimental platforms such as semiconductor nanowires, two-dimensional electron gases, and topological insulators and holds relevance for topological superconductivity and quantum computation.

Straight Indium Antimonide Nanowires with Twinning Superlattices via a Solution Route.

Indium antimonide (InSb) enables diverse applications in electronics and optoelectronics. However, to date, there has not been a report on the synthesis of InSb nanowires (NWs) via a solution-phase strategy. Here, we demonstrate for the first time the preparation of high-quality InSb NWs with twinning superlattices from a mild solution-phase synthetic environment from the reaction of commercial triphenylantimony with tris(2,4-pentanedionato)-indium(III). This reaction occurs at low temperatures from 165 to 195 °C (optimized at ∼180 °C), which is the lowest temperature reported for the growth of InSb NWs to date. Investigations reveal that the InSb NWs are grown via a solution-liquid-solid (SLS) mechanism due to the catalysis of the initially formed indium droplets in the mild solution-phase reaction system. The twinning superlattices in the InSb NWs are determined with a pseudoperiodic length of ∼42 monolayers, which result from an oscillating self-catalytic growth related to the periodical fluctuation between reduction rate of In and Sb sources in the route. The optical pump-terahertz probe spectroscopic measurement suggests that the InSb NWs have potential for applications in high-speed optoelectronic nanodevices.